I. Field of the Invention
The present invention relates to sample handling apparatus and, more particularly, to apparatus for circulating sample holders in a storage compartment past an operating station. The invention is particularly well suited for handling samples which, after stabilization at the operating station, are removed from the storage compartment, operated upon, and then returned to the compartment.
II. Description of the Prior Art
U.S. Pat. No. 3,859,528 (Luitweiler et al., issued Jan. 7, 1975) illustrates a prior commercial sample handling apparatus for circulating a plurality of sample holding vials past an operating station. The vials are supported within respective compartments of multi-compartment sample holding trays and the trays are circulated in rectilinear fashion around the sample storage compartment of the apparatus. At the operation station an elevator removes a vial, positions it in a radiation detection chamber for analysis, and then returns the vial to the compartment. To this end the sample storage compartment is loaded with two longitudinally extending, generally parallel columns of trays on opposite sides of the operating station. Longitudinally movable fingers at opposite ends of each column increment the entire column of trays longitudinally a distance of one tray depth to drive trays in the first column toward the operating station and trays in the second column away from the operating station. After incrementing each column of trays, trays at the remote ends of the columns are indexed laterally from one column to the other after which the fingers again increment the columns one tray depth.
While the foregoing apparatus functions reasonably well for the purpose intended, it suffers from a number of inherent drawbacks which reduce its overall commercial attractiveness. First, because of the limited longitudinal drive capabilities of the incrementing fingers, incremental movement of each tray column requires that each tray abut an adjacent tray so that the trays can increment each other serially in domino fashion. As a result, if the apparatus does not contain a full load of trays, the incrementing fingers are unable to longitudinally increment the tray columns to positions wherein the trays at the remote ends of the columns may be laterally indexed between columns. In addition, when indexing, the apparatus may fail to accurately align a tray in position over the elevator at the operating station. In such a case the elevator, instead of engaging and removing the sample vial, will instead strike the tray and cause the apparatus to jam. Further, there is no provision in the prior apparatus for detecting or signalling the occurrence of the foregoing malfunctions.
Accordingly, a need exists for a more versatile sample handling apparatus exhibiting the advantages of the prior apparatus but without the disadvantages thereof. Thus, a need exists for apparatus which is capable of circulating any number of sample holders from one to a full load and which is capable of accurately stabilizing each sample holder as it moves to and away from and while at an operating station.